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Posted 18 Aug 2001
Licenced CPOL

CNumSpinCtrl - a simple numeric spin control

, 11 Jul 2002
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Numeric spin control for working with real numbers


When I needed a numeric spin control, I searched both CodeGuru and CodeProject. Surprisingly I only found one article by T. VU KHAC on CodeGuru, but as it turned out his CNumSpinCtrl could only be used in pair with CNumEdit which was too restrictive for my purposes. So I ended up writing my own numeric spin control.

CNumSpinCtrl allows you to work with non-integer numbers quite easily. It provides methods to set up value range, increment, and current position. It also lets you format the output value either by specifying number of decimal places or by providing your own formatting string.


Using the control is not much different from using CSpinButtonCtrl. You would subclass a dialog item or create the control dynamically. Then all you need to do is to set up range and position and, if necessary, the output formatting. Here’s an example from the demo project:

BOOL CCNumSpinCtrlDemoDlg::OnInitDialog()
        m_spinValue.SetDecimalPlaces (3);
        m_spinValue.SetTrimTrailingZeros (FALSE);
        m_spinValue.SetRangeAndDelta (0.1, 1.0, 0.05);
        m_spinValue.SetPos (0.5);

There one thing to watch out however - style. Make sure you uncheck the "Set buddy integer" style or, if you are creating control dynamically, do not add UDS_SETBUDDYINT style. Otherwise the Windows automatically resets buddy's value to some integer when user clicks up/down arrows.


There are two ways to format the output value: by specifying a number of decimal places or by providing a formatting string. With the first method you will specify number of decimal places with a call to SetDecimalPlaces function. Passing -1 to this function will turn off rounding to decimal places (the value will be output with "%g" format string). You can also specify whether you want to trim any trailing zeros with a call to SetTrimTrailingZeros. With a second method you simply provide your own formatting string, which later will be used with CString’s Format function. Example:

SetFormatString ("%.2e")


Be sure to set appropriate formatting settings. If your formatting settings are inadequate for the current range and increment, the text in the buddy control may not change at all. For example, if you set the increment to be 0.005, but the number of decimal places only to 1, the value in buddy control will not change when a user clicks on up and down arrows. This is because the control does not keep the current value internally. The value is obtained from the buddy control before it is incremented or decremented. Then it is formatted and passed back to the buddy control. So the formatting settings are quite important.


2002-07-03 Commented out ModifyStyle in InitControl - it didn't work, didn't remove UDS_SETBUDDYINT style. Put ASSERT instead. So now program will ASSERT if you forget to remove UDS_SETBUDDYINT style in resources.
Fixed wrapping. In some cases due to poor machine precision the wrapping condition didn't evaluate properly.
2002-06-05 Warren Stevens added wrapping ability. If the style of the spin control is set to "wrap", the value will wrap around if increased or decreased past the range limits.
2002-04-17 Fixed bug with trimming zeros. If number of decimal places was set to zero, it was still trimming zeros (e.g. 100 would become 1).
2001-08-24 Changed ON_NOTIFY_REFLECT to ON_NOTIFY_REFLECT_EX so that parent can also handle notification message from spin control. Thanks to Emmanuil Tsagarakis for this one.
2001-07-06 Original version.


This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


About the Author

Damir Valiulin
Software Developer
Canada Canada
No Biography provided

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Comments and Discussions

GeneralRe: Small bug found -> correction Pin
tattalevieuxgrincheux16-May-03 11:30
membertattalevieuxgrincheux16-May-03 11:30 
GeneralRe: Small bug found -> correction Pin
Damir Valiulin16-May-03 12:55
memberDamir Valiulin16-May-03 12:55 
GeneralRe: Hi Pin
Young-Dae, Choi26-Aug-03 5:01
memberYoung-Dae, Choi26-Aug-03 5:01 
GeneralNice class...thanks! Pin
11-Jun-02 7:52
suss11-Jun-02 7:52 
GeneralProject does not build Pin
Julia Larson9-Feb-02 21:34
memberJulia Larson9-Feb-02 21:34 
GeneralRe: Project does not build Pin
10-Feb-02 6:16
suss10-Feb-02 6:16 
GeneralRe: Project does not build Pin
Trollslayer13-May-03 3:57
mentorTrollslayer13-May-03 3:57 
GeneralRe: Project does not build Pin
ChinaThink28-Aug-03 15:57
memberChinaThink28-Aug-03 15:57 

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